I think BT's got me the most excited, but watching it again after all this time, it might simply be because it was the first trailer to implement machinima, so it felt different than what we'd seen before; it made it feel more important.

Ulduar, mostly because they actually made some decent faces for Rhonin, Thrall, Garrosh and Jaina.

Especially the Jaina and Garrosh face would be so much better than the current ones, you could actually see some expressions there instead of those Derp Faces they currently have.

Too often, we are mistaken for druidic types. perhaps that's true for some shaman, but do not let yourself be plagued by the ignorant belief that we are always peaceful.
Nothing about what I do is harmonious. I command the elements to my will. There is nothing offered in return. I would have it no other way.

the Zul'Aman trailer is awesome, "we gonna bury you er".
the fall of the lich king comes after, the scene with king Terinus and all the people Arthas killed really harkened back to WCIII
after that id have to say the thunder king. Cho's poem really struck me, "gather heros, sound the drums....the thunder king comes..."